1. Field of the Invention
This invention relates to the preparation of polyisocyanurate polymers such as polymer foams, and is more particularly concerned with use of a class of catalyst which promote the trimerization of polyisocyanates to polyisocyanurate polymers.
2. Description of the Prior Art
Polyisocyanurate polymers such as rigid polyisocyanurate foams are known in the art. The prior art discloses methods for preparing such polymers by reacting an organic polyisocyanate with a polyether or polyester polyol utilizing a polyisocyanurate group formation catalyst. Foams are prepared by effecting such reaction in the presence of a blowing agent. In the optimum situation the isocyanurate catalyst utilized promotes formation of both isocyanurate linkages and urethane linkages to produce urethane-modified polyisocyanurate polymers. See, for example, U.S. Pat. Nos. 3,516,950; 3,580,868; 3,620,986; 3,625,872; 3,635,848; 3,725,319; and 3,745,133.
Compounds which are known as catalysts for polyisocyanurates are the N-alkali metal and N-alkaline earth metal compounds of primary and secondary aliphatic, araliphatic, aromatic amines and heterocyclic amines. Amines which may be employed are, for example, methylamine, N-butylamine, tert.-butylamine, methoxy-n-propylamine, oleylamine, diethylamine, di-n-butylamine, diisobutylamine, dicyclohexylamine, N-methylstearylamine, benzylamine, ethylbenzylamine, dibenzylamine, phenylbenzylamine, aniline, naphthylamine, 3-N-ethylaminotoluene, toluidine, methylaniline, N-isobutylaniline, diphenylamine, N-methylanisidine, and also pyrrolidine, piperidine, 1,2,3,4-tetrahydroquinoline, pyrrole, indole, 2-methylindole, 2,3-dimethylindole, 5-methoxy-2,3-dimethylindole, carbazole, 3,6-dinitrocarbazole, N,N'-dimethylethylenediamine and N,N'-dimethyl-p-phenylenediamine.
N-alkali metal and N-alkaline earth metal compounds of carboxylic acid amides are also known catalysts. These include aliphatic and aromatic carboxylic acid amides and also such cyclic acid amides as imides and lactams. The following compounds are examples of compounds suitable for the production of such N-metal compounds: acetamide, trimethylacetamide, myristinic acid amide, stearoyl amide, N-methylacetamide, phenylacetamide, benzamide, N-alkyl benzamides, succinimide, tetrapropenyl succinimide, phthalimide, pyrrolidone, butyrolactam, caprolactam, phthalimidine and saccharine.
Also, as catalysts alkali or alkaline earth metal may be combined with the amines or carboxylic acid amides such as, for example, lithium, sodium, potassium, magnesium, barium, and calcium, with the preferred metals being lithium, sodium, potassium and calcium.
Also, alkali or alkaline earth metal salts of carboxylic acids are useful as catalysts for isocyanurate polymers.
The catalyst of this invention do not contain alkali or metals and provide an unexpected beneficial delay in the isocyanurate reaction which aids in processing. This delay is especially helpful where molding is undertaken. The catalyst herein also gives a complete product cure.